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Cardiff University (2020)

A parametric investigation of natural ventilation retrofit strategies for the cosmopolitan heritage buildings of Alexandria

Taher, Ahmed Kamal

Titre : A parametric investigation of natural ventilation retrofit strategies for the cosmopolitan heritage buildings of Alexandria

Auteur : Taher, Ahmed Kamal

Etablissement de soutenance : Cardiff University

Grade : Doctor of Philosophy (PhD) 2020

Résumé
The impacts of political, economic and social changes in Egypt during the second half of the twentieth century put its distinctive architectural heritage at risk. The Mediterranean city of Alexandria is a case in point, its existing heritage buildings having endured many levels of relapse in the form of neglect, misuse and demolition in favor of new-build concrete blocks, which are assumed to better meet modern standards of climatic comfort. Heritage buildings are an important aspect of any city in their capacity to provide cultural reference points. Demonstrating capacity for better levels of energy efficiency and thermal comfort has become a critical challenge to such buildings’ survival. Previous heritage retrofit research to date, has been more influenced towards cold climates in Europe and north America. However, different climatic conditions and building styles raise other issues. From an architectural perspective, the European style courtyarded buildings that established the nineteenth-century heritage fabric of Alexandria theoretically offer good potential for healthy indoor air replacement, while the Mediterranean climate of the city provides enhanced possibilities for promoting indoor thermal comfort. Yet observation of these heritage buildings demonstrates that occupants today rely heavily on energy consuming mechanical ventilation systems. The principal aim of this thesis is to evaluate a range of potential retrofitting strategies for improving natural ventilation performance and thermal comfort of the typical nineteenth century listed residential buildings located in the heritage district of Alexandria. This thesis aims to establish a rationale for the sustainable conservation and the potential for the passive upgrading of Alexandrian built heritage to better meet performance targets. This is achieved by applying different research methods to address the various values at stake. These methods include historical analysis, values-based theoretical positioning and practical assessment in the form of both measured field data, and scientific modelling (computational fluid dynamics). There are four stages in this thesis : firstly, it identifies the significance and key problems facing the heritage context of Alexandria, the impact of its climate conditions and the applicability of natural ventilation strategies. From this a representative case study is selected. Secondly, a review of heritage retrofitting research projects is used to establish how and to what extent those practices can be transferred to the Alexandrian heritage context. Thirdly, the potential for natural ventilation in the case study was evaluated using computational fluid dynamics. Finally, a proposed parametrical study was formulated using the selected natural ventilation design measures based on the literature review and ii considering the evaluation study results. The effectiveness in terms of enhancing natural ventilation performance was quantified using “ANSYS Fluent”. The findings show a detailed natural ventilation deficiency performance in the case study building with an average internal airflow magnitude of 0.22 m/s as modified today. However, the study indicates potential for future improvement. The parametrical simulations indicate that the proposed measures can significantly enhance the natural ventilation performance inside the case study building. This in turn increases the potential for providing internal thermal comfort. This investigation of a typical building aims to contribute to the understanding of conservation approaches that not only preserve a building’s cultural value but also reclaim its natural ventilation performance.

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Page publiée le 21 avril 2021